CSM turnaround

Having separated from the Saturn, the CMP continued thrusting forward, controlling with the translational hand controller, until the EMS indicated that he had gained a speed of half a foot per second. Then, once enough time had elapsed to ensure that the CSM was well clear of the third stage, he pulled back on the rotational control in his right hand. A different pattern of thrusters fired and the CSM began a half turn, pitching up the nose of the spacecraft until it pointed at the lunar module nestled in the top of the spent rocket. The LM's docking port was at the top of the lander while the CSM's was built into the apex of the command module, and the turnaround had brought the two ports face to face. It was only a matter of flying slowly towards the LM to bring them towards final docking.

One reason for using the EMS was because the crew could not see whether the spacecraft had cleared the third stage, and it was felt safer to rely on empirical measurement rather than guesswork. Not all the crews agreed with this approach. In his post-flight debrief, Richard Gordon of Apollo 12 felt the EMS got in the way. "If I'd been smart and used my head, I'd have taken these TD&E procedures and scratched all reference to the EMS whatsoever."

Both he and his commander Pete Conrad felt that it would have been enough simply to fire the thrusters for a set period of time, thereby simplifying the procedures. "That's exactly what I would have done,'' continued Gordon. "I would have separated from the SLA. I'd have thrust forward for the time to get 0.8 feet per second. I'd have waited to 15 and I would have backed off thrusting for a couple more seconds. And that's all you need.'' An additional problem using the EMS was that it could not track the delta-v very well if the CSM was rotating, or was subjected to shock, both of which were happening in this task. Having set the display to read minus 100, Gordon found it had jumped to read minus 98 when he was expecting a reading over 100. "So I had no idea how much velocity I'd put in to the thing and I just continued thrusting forward for a few seconds, probably being conservative because I wanted to make sure I got far enough away from the booster before we did the turnaround.''

When the pyrotechnics fired to separate the CSM from the launch vehicle and to cut the SLA into four, a lot of debris could be generated, as many Apollo crews noted. Even before Apollo 17's CSM America had turned around to face the LM Challenger, Ron Evans exclaimed, "My gosh, look at the junk!"

By the time of this final Moon mission, the procedures for separation were well rehearsed. Evans let the CSM drift out for a few seconds. "Okay; there's 15 seconds. Pitch her up.'' As the spacecraft came around to view the S-IVB, Eugene Cernan spotted the debris surrounding it, "Houston, we're right in the middle of a snowstorm.''

"Roger," confirmed Capcom Bob Parker. "And we'd like Omni Delta.'' The rotation of the CSM meant that the omnidirectional antenna they were using was no longer well placed and they needed to switch to another to maintain communication. He wasn't particularly interested in the debris.

"And there goes one of the SLA panels,'' called Cernan.

"Yes," agreed Evans as they continued rotating. "We're not there yet. Long ways to go yet.''

"There goes another SLA panel, Houston, going the other way,'' said Cernan.

Jack Schmitt had his own windows to look out of. "Hey, there's the booster!'' he yelled as the S-IVB came into view.

"Roger," said Parker. "Bet you never saw the SLA panels on the simulator."

Apollo 15's lunar module still within the S-IVB and surrounded by a cloud of particles.

Apollo 15's lunar module still within the S-IVB and surrounded by a cloud of particles.

Cernan agreed. "No, but we've got the booster and is she pretty? Challenger's just sitting in her nest.'' "Roger. We'd like Omni Bravo, now, Jack," requested Parker.

Cernan had been watching the particles that were floating outside his window. "And, Houston, some of the particles going by the window fairly obviously seem to be paint.''

Once the CSM had turned around to face the LM, the rotation was stopped. Then, by pushing on the translational hand controller, the CMP could kill the drift away from the third stage and start to approach. As the two spacecraft slowly came together, he had to keep them aligned. To aid him, he had an optical aid, known as the crewman optical alignment sight (COAS), which was rather like a gun sight.

It was mounted in the forward-facing window on the left and it gave him a consistent line of sight. A 'stand-off target was mounted on the LM, appropriately positioned so that the combination of the COAS and the docking target allowed him to adjust for left/right, up/down and angle of approach to bring the two spacecraft accurately together.

Ken Mattingly was surprised at how easy this manoeuvre proved to be - a testament to the fidelity of the simulations prior to the flight. ''When we pitched over, the crosshairs on the COAS were almost exactly centred on the target. It was just a matter of pushing it, sitting there, and waiting for the two to come together. I made one lateral correction and one vertical correction. We didn't do another The target on Apollo 12's LM guided Richard thing until contact.'' Gordon to an accurate docking.

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